Maggini Ivan, Cardinale Massimiliano, Favaretto Andrea, Voříšek Petr, Spina Fernando, Maoret Francesco, Ferri Andrea, Riello Sara, Fusani Leonida
Austrian Ornithological Centre Konrad-Lorenz Institute of Ethology University of Veterinary Medicine Vienna Wien Austria.
Department of Aquatic Resources Institute of Marine Research Swedish University of Agricultural Sciences Lysekil Sweden.
Ecol Evol. 2020 Dec 19;11(2):967-977. doi: 10.1002/ece3.7110. eCollection 2021 Jan.
Europe has a well-established network of breeding bird monitoring that is used to produce supranational indices of population trends for many species. However, a comparison of breeding bird censuses with other methods may be beneficial to confirm the validity of such indices. The aim of this study was to assess the value of standardized capture data of migratory birds at migration bottlenecks as an indicator of the effective breeding populations. One limitation to this method is that several populations are co-occurring at these bottlenecks and their catchment areas need to be clearly identified to allow extrapolation of population indices. Here, we used standardized trends in capture numbers of 30 species on the island of Ponza, a migration bottleneck in the central Mediterranean, and compared them to population trends estimated in the putative catchment breeding areas between 2005 and 2016. The catchment areas were identified through the analysis of ring recoveries during the breeding season of birds passing through Ponza. Our results show an agreement between the population trends observed on Ponza and those in the breeding areas in 15 out of 30 species. The correlations were strongest in species with a more robust definition of the catchment areas, that is, species with more than 10 recoveries, and for which the recoveries were most likely of breeding birds. The main reason for disagreement between the two indices in the remaining species might be related to different intensity of sampling in different areas. This issue can be solved by further developing monitoring projects in underrepresented countries, as well as by intensifying monitoring through ringing, both in the breeding grounds and at migration bottlenecks. These results show that spring migration monitoring at bottlenecks has the potential to provide a valuable complement and an independent control of breeding bird surveys, allowing raising early warnings of population declines and contributing to their conservation.
欧洲拥有完善的繁殖鸟类监测网络，用于生成许多物种的超国家种群趋势指数。然而，将繁殖鸟类普查与其他方法进行比较可能有助于确认此类指数的有效性。本研究的目的是评估在迁徙瓶颈处对候鸟进行标准化捕获数据作为有效繁殖种群指标的价值。该方法的一个局限性是，在这些瓶颈处有几个种群同时出现，需要明确识别它们的集水区，以便推断种群指数。在此，我们使用了地中海中部迁徙瓶颈蓬扎岛上30种鸟类的标准化捕获数量趋势，并将其与2005年至2016年期间在假定的集水区繁殖区域估计的种群趋势进行比较。通过分析在繁殖季节经过蓬扎的鸟类的环志回收情况来确定集水区。我们的结果表明，在30种鸟类中，有15种在蓬扎观察到的种群趋势与繁殖区域的趋势一致。对于集水区定义更明确的物种，即环志回收超过10次且回收的很可能是繁殖鸟类的物种，相关性最强。其余物种的两个指数不一致的主要原因可能与不同地区的采样强度不同有关。这个问题可以通过在代表性不足的国家进一步开展监测项目来解决，也可以通过在繁殖地和迁徙瓶颈处加强环志监测来解决。这些结果表明，在瓶颈处进行春季迁徙监测有可能为繁殖鸟类调查提供有价值的补充和独立对照，从而能够对种群数量下降发出早期预警并有助于其保护。
